Type A Hepatitis has been extensively studied in susceptible chimpanzees. To date, the chimpanzee remains the species most susceptible to infection with this virus. Attempts to infect other non-human primate species with this virus are in progress. Studies of type B Hepatitis have also been carried out in chimpanzees. Vaccinated animals rechallenged with live Hepatitis B virus showed solid immunity to the infection. Saliva from three patients that were chronic carriers of B Hepatitis were pooled and inoculated into a chimpanzee. This animal developed type B Hepatitis, proving that non-percutaneous spread of Hepatitis B virus is possible.